function [image, imageSize] = loadEnviData( fname )
% loadEnviData         - read envi image 
%
%  Reads an image of ENVI standard type 
%  to a [col x line x band] MATLAB array
% image=loadEnviData(fname)
% [image,imageSize]=loadEnviData(fname)
%
% INPUT :
%
% fname string giving the full pathname of the ENVI image to read.
%
% OUTPUT :
%
% image----------- c by l by b array containing the ENVI image values organised in
%    c : cols, l : lines and b : bands.
% imageSize         the [3,1]  size matrix of the image
% imageSize(1): the number of columns; imageSize(2): the number of lines;
% imageSize(3): the number of bands
%
% NOTE :    freadenvi needs the corresponding image header file generated
%    automatically by ENVI. The ENVI header file must have the same name
%    as the ENVI image file + the '.hdf' exention.
%
%%%%%%%%%%%%%

% Check user input
 if ~ischar(fname)
    error('fname should be a char string');
 end
    
% Parameters initialization
elements={'samples ' 'lines   ' 'bands   ' 'data type '};
d={'bit8' 'int16' 'int32' 'float32' 'float64' 'uint16' 'uint32' 'int64' 'uint64'};

% Open ENVI header file to retreive s, l, b & d variables
rfid = fopen(strcat(fname,'.hdr'),'r');
    
% Check if the header file is correctely open
if rfid == -1
   error('Input header file does not exist');
end

% Read ENVI image header file and get p(1) : nb samples,
% p(2) : nb lines, p(3) : nb bands and t : data type
while 1
     tline = fgetl(rfid);
     if ~ischar(tline), break, end
     [first,second]=strtok(tline,'=');
    
     switch first
        case elements(1)
            [f,s]=strtok(second);
            p(1)=str2num(s);
         case elements(2)
            [f,s]=strtok(second);
            p(2)=str2num(s);
         case elements(3)
             [f,s]=strtok(second);
             p(3)=str2num(s);
         case elements(4)
             [f,s]=strtok(second);
             t=str2num(s);
             switch t
                case 1 
                    t=d(1);
                case 2 
                    t=d(2);
                case 3 
                    t=d(3);
                case 4 
                    t=d(4);
                case 5 
                    t=d(5);
                case 12 
                    t=d(6);
                case 13 
                    t=d(7);
                case 14 
                    t=d(8);
                case 15
                    t=d(9);
                otherwise error('Unknown image data type');
             end
        end
end
fclose(rfid);

t=t{1,1};
% Open the ENVI image and store it in the 'image' MATLAB array
disp([('Opening '),(num2str(p(1))),('cols x '),(num2str(p(2))),('lines x '),(num2str(p(3))),('bands')]);
disp([('of type '), (t), (' image...')]);
fid=fopen(fname);
image=fread(fid,t);
image=reshape(image,[p(1),p(2),p(3)]);
fclose(fid);
imageSize=p;
    


